This invention relates in general to embroidering machines and to a new and useful mechanism for moving a workpiece carrier in respect to an embroidery head in respect to one or more coordinates which includes a disengageable clutch mechanism.
In multi-head embroidering machines, the material to be embroidered is clamped in circular or oval embroidery frames which are secured to a work carrier common to all the embroidery frames. To embroider borders, a frame encompassing all the embroidering heads and having no strutting in the embroidering area is employed instead of the circular or oval embroidery frames, or a plurality of embroidery frames is used extending over two or more embroidering heads.
Particularly if patterns with a small number of stitches are to be made, the embroidery frames must be exchanged for other frames, already prepared outside the machine, within relatively short periods of time, and each individual exchange frame must be secured to the work carrier separately, by means of knurled-head screws. The frequent exchange requires laborious finger work and time, and may quite considerably reduce the efficiency of the machine. A certain improvement has been obtained by substituting spring operated snap-action mechanisms for the screws (German Pat. No. 17 60 399 and German utility model 78 23 922), however, only small-size circular or oval embroidery frames can be secured in this way with a satisfactory reliablity. For clamping substantially larger border embroidery frames, the prior art snap mechanisms are unsuitable. Consequently, border embroidering frames have to be fixed to the driven work carriers, or to a carrier rail, by means of screws as before.
A prior art multi-head embroidering machine is disclosed in German AS 27 45 396, for example. In this design, the embroidery frames are exchangeably secured to a carrier rail which extends over all of the embroidery heads and is in turn firmly connected, through a plurality of struts, to a well known pantograph bar by which the embroidery frames are moved beneath the embroidering heads in accordance with the desired pattern, in the directions perpendicular to each other. On the underside of the pantograph bar, mutually perpendicular guide rails are provided which are received without play each between two ball bearings mounted on drive slides for rotation about fixed shafts forming the output sides of a coordinate control device. The pantograph bar has a hollow rectangular cross section, with a downwardly open slot therethrough. The lower horizontal legs engage the ball bearings from below and project into grooves of the drive slides. The pantograph bar forms a part of the coordinate control device and, as mentioned above, it is firmly connected to the rail carrying the embroidery frame, through a plurality of relatively long struts. This strutting of the pantograph bar to the carrier rail must be made relatively massive, thus the masses to be moved must be augmented, if a stability for high embroidering speeds and exactly made patterns is sought.